Deuteronomy 20:16-20 - Laws Concerning War With Canaanite Nations

¹⁶ But of the cities of these peoples, that LORD thy God gives thee for an inheritance, thou shall save alive nothing that breathes, ¹⁷ but thou shall utterly destroy them--the Hittite, and the Amorite, the Canaanite, and the Perizzite, the Hivite, and the Jebusite--as LORD thy God has commanded thee, ¹⁸ that they not teach you to do after all their abominations, which they have done to their gods, so ye would sin against LORD your God.

¹⁹ When thou shall besiege a city a long time, in making war against it to take it, thou shall not destroy the trees of it by wielding an axe against them, for thou may eat of them. And thou shall not cut them down, for is the tree of ²⁰ Only the trees of which thou know that they are not trees for food, thou shall destroy and cut them down. And thou shall build bulwarks against the city that makes war with thee, until it falls.